Bow hunter’s syndrome unmasked after contralateral vertebral artery sacrifice for aneurysmal subarachnoid hemorrhage

Abstract

Bow hunter’s syndrome (BHS), or positional vertebrobasilar insufficiency, is a rare disorder characterized by positional stenosis or occlusion of the dominant vertebral artery (VA) with concordant signs and symptoms of brainstem ischemia. Many etiologies have been described, with the most common level of obstruction occurring at the craniocervical junction. The authors report acquired BHS after the patient’s contralateral VA was sacrificed for ruptured aneurysm. A 44-year-old man was referred to our institution for years of continued positional tinnitus, vertigo, and nausea. This symptomatology began 5years prior, immediately after the patient’s right VA was endovascularly sacrificed to treat a ruptured VA aneurysm. From the time of treatment, right head turning caused instantaneous symptoms consistent with brainstem ischemia. Evaluations performed during the 5year interim before referral included computed tomography angiography, MRI, and diagnostic cerebral angiography (DCA). All failed to identify a causal etiology. A diagnosis of BHS was made with dynamic DCA. With the patient’s head turned to the right, angiography of the left VA demonstrated a positional block. The patient underwent left VA decompression. Intraoperative dynamic DCA was utilized to demonstrate adequacy of decompression. The patient tolerated the procedure without complication. Symptomatology immediately completely subsided and remained absent at his 3month follow-up. An acquired BHS should be recognized as a possible complication if VA sacrifice is considered for an unclippable or uncoilable aneurysm.